There are many types of welding electrodes, each with its application scope, and whether the use of welding electrodes is appropriate has a great impact on welding quality, labor productivity and product costs. Generally, it should be based on the chemical composition, mechanical properties, weldability, working environment (with or without corrosive medium, high temperature, low temperature, etc.) requirements of the constituent structural steel, the shape (rigidity) of the welded structure, the force, and the welding equipment DC welding machine) and other aspects are comprehensively considered to decide which electrode to use.The factors to consider when selecting are:
Mechanical properties of weldments
Low-carbon steel, medium-carbon steel, and low-alloy steel can be selected according to their strength grades. When the welding structure has high rigidity and complicated stress conditions, a lower-level electrode should be used. After the strength of the electrode is determined, the decision to use an acidic or alkaline electrode depends mainly on the complexity of the specific shape of the welding structure, the thickness of the steel (that is, the stiffness), and the load of the weldment (static or dynamic). , The crack resistance of steel and the difficulty of obtaining DC power. Generally speaking, the requirements for plasticity, impact toughness and crack resistance are high. Welding electrodes working at low temperatures should use alkaline electrodes. When restricted by certain conditions and unable to clean the rust, oil and oxide scales on the cracks of the low-carbon steel weldment, acid electrodes with low sensitivity to rust, oil and oxide scale and strong anti-porosity performance should be selected. For welding of dissimilar steels, such as welding of low-carbon steels and low-alloy steels, and low-alloy steels of different strength grades, generally, electrodes that match the lower strength grades of steel are used.
Weldment working conditions
For welding parts that have specific requirements for the working environment, corresponding welding electrodes should be selected, such as: low temperature electrodes, underwater electrodes, etc. Pearlite heat-resistant steel is generally selected by the electrode with a chemical composition similar to that of steel, or according to the operating temperature of the weldment.
"E4313" electrode (such as: J421, J421X, J421Fe, etc.) should be used for thin plate welding or spot welding. This electrode is not easy to burn through and easy to arc. On the premise of satisfying the performance of the welding piece and the operating performance of the electrode, a large specification and high efficiency electrode should be selected. When the performance is basically the same, the electrode with a lower price should be selected as much as possible to reduce the production cost.
Sometimes in order to ensure the quality of the weldment, it is necessary to finalize it by welding tests. In addition, from the perspective of welder health, acid welding electrodes should be used whenever possible.